Cover image for The runaway universe : the race to find the future of the cosmos
The runaway universe : the race to find the future of the cosmos
Goldsmith, Donald.
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Cambridge, Mass. : Perseus Books, 1999.

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x, 232 pages : illustrations ; 25 cm
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QB981 .G597 2000 Adult Non-Fiction Central Closed Stacks
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For decades, astronomers have sought to discover the ultimate fate of the univers. Will the cosmos continue forever in its expansion, which began billions of years ago with the big bang? Or will gravity someday reverse the process, producing a "big crunch?" Within the past few years, two rival groups of astronomers have announced a discovery that seems to resolve the issue: Instead of slowing down, the expansion of the universe seems to be accelerating . This finding has shaken the science of cosmology to its very foundation. This is the story of the astronomers who have stood the world of cosmology on its ear--and of their competitive race to discover the future of the cosmos. It is also an investigation into whether their remarkable findings will stand the test of time. If the new results are verified in the coming years, we will eventually find ourselves in a "runaway universe," in which every bit of matter is extremely far from its closest neighbor. Then the cosmological constant, which Einstein once rued as his "greatest blunder," will turn out to be one of his finest insights into the nature of space itself.A vivid picture of an unexpected turn of events, The Runaway Universe presents the startling new discovery that is revolutionizing our view of the cosmos.

Reviews 4

Booklist Review

Since Edwin Hubble discovered in the 1920s that the universe is expanding and that a galaxy's recessional velocity increases in proportion to its distance from the Milky Way, cosmologists have wondered how long the expansion will continue. The answer depends on the density of matter. If density sinks below a critical value, the answer is forever, a scenario fascinatingly imagined in The Five Ages of the Universe by Fred Adams and Greg Laughlin [BKL Ap 15 99]. Goldsmith, in an equally exciting explication, presents the refinements astronomers have made since Hubble's discoveries in measuring both the density and the expansion rate. He delves into the extraordinary proposition advanced in 1998 and 1999 by two groups of astronomers that the expansion rate is increasing. They concluded this because of improvements in estimating the billions-of-light-years distances to galaxies, using as rulers the brightness of supernovae that burst within them. Wrapping up the technical observational advances with Einstein's "cosmological constant," which can imply an increasing expansion rate, Goldsmith packages a story astro fans will open eagerly. --Gilbert Taylor

Publisher's Weekly Review

It could be even bigger than we thought: not only is the universe expanding (as astronomers have long known) but its rate of expansion is increasing. Observations of supernovas in 1998, if accurate, show that the cosmos is spreading and dispersing. In a neat, up-to-date introduction to cosmology and astrophysics, prolific astronomy popularizer Goldsmith (The Astronomers; The Hunt for Life on Mars) explains how the universe might be "shaped" and why its sped-up growth is such a surprise. Einstein's theories introduced a number called the cosmological constant: if that number had a certain (below-zero) value, the universe would stay the same size. Recent models of the expanding universe set Einstein's constant at zero. Now it turns out the constant has a value above zero. On his way toward the new science of supernovae, Goldsmith covers Einstein and general relativity, telescope maestro Edwin Hubble and his rival Harlow Shapley, such 1980s quantum theorists as Alan Guth and the mysterious "dark matter" dispersed through intergalactic space. It turns out that "all the structure in the cosmos has grown from tiny fluctuations in the density of matter from place to place"; moreover, we live in a 10-billion-year window of cosmological history during which space is curved, but not too curved--earlier or later, life could never arise. Outlining these theories and discoveries, Goldsmith can sound like a stage magician: his new knowledge "will prove so amazing that your friends and family will doubt what you have to tell them." On the other hand, he's exceptionally good at explaining math in layperson's terms--a talent welcome in a complicated subject such as this. (Jan.) (c) Copyright PWxyz, LLC. All rights reserved

Library Journal Review

The universe has been expanding ever since the Big Bang, but gravity is slowing its expansion over time. So held conventional astronomical wisdom until 1998, when two teams of researchers presented data indicating that the expansion of the universe is actually accelerating under the influence of a mysterious antigravity force. How the scientists reached their astonishing conclusion, and how they might in turn be proved wrong, is the subject of this book. Goldsmith, an astronomer and science writer (Einstein's Greatest Blunder?), has received awards for popularizing astronomy. His text is well organized and at times witty. But this is one of his less accessible works; before settling down with it, readers would benefit from completing an undergraduate-level introductory astronomy course, and the math-shy will find it downright intimidating. Recommended for academic libraries.--Nancy Curtis, Univ. of Maine Lib., Orono (c) Copyright 2010. Library Journals LLC, a wholly owned subsidiary of Media Source, Inc. No redistribution permitted.

Choice Review

In the second half of the 20th century, the working hypothesis of cosmologists was that we live in a universe that is expanding, but that the expansion is slowing. The expansion would eventually stop, and the universe might even begin to contract. Better observations, expected to be produced by the marvelous instruments being introduced, would allow measurement of the characteristics of the expansion, and thus a prediction of the future evolution of the universe. However, as writer Goldsmith describes, the observations may be taking us in a completely different direction. In a lucid exposition of the data and the theory, Goldsmith presents the possibility that the universe is expanding at an accelerating rate, and that a famous constant of general relativity, once thought to be identically zero, may have a value nearer to one. The subject is difficult and the arguments subtle, yet the book is so well written that the lay reader will be able to achieve an understanding of the issues and of the profound philosophical implications arising from them. It is early in the revolution, as Goldsmith points out, and astronomers continue to weigh the evidence, but the book is a thoughtful and balanced introduction to these fascinating ideas. General readers; lower-division undergraduates. D. E. Hogg; National Radio Astronomy Observatory



Chapter One The Runaway Universe Imagine a strange universein which the expansion of the cosmos, instead of being slowed by gravity, undergoes a continuous acceleration from the presence of a mysterious form of energy. This energy, concealed from any direct detection by its complete transparency, permeates seemingly empty space, furnishing the cosmos with a "free lunch" of just the sort that old wives' tales forbid. Just as amazingly, every cubic centimeter of the new space that the ongoing cosmic expansion creates likewise teems with this invisible energy, the existence of which endows each volume of space with a tendency to expand. As a result, the universe multiplies its energy content many times over as time goes by. The increase in its hidden energy makes the universe accelerate ever more rapidly, eventually driving its basic units of matter to utterly unfathomable separations. Instead of a chance to contract, perhaps to recycle itself through another big bang, this universe faces a future in which all cosmic distances grow to billions of times their present immense values. As this happens, the average density of matter in the cosmos falls ever more rapidly toward zero, because the energy of empty space makes the universe expand at a continuously increasing rate.     This parallel universe is our own--if astronomers have correctly interpreted their recent observations. They have known for seventy years that the universe is expanding: Clusters of galaxies, each a giant agglomeration of matter containing billions upon billions of stars, are moving away from one another throughout all of space. Indeed, space itself must be expanding, carrying the galaxy clusters with it. This cosmic expansion implies that the universe began, at least in its present phase, at a time when all the matter (and all space, too!) existed at a moment of near-infinite temperature and density, which astronomers call the "big bang." Ever since the big bang, now estimated to have occurred about 14 billion years ago, the universe has cooled while expanding. This cooling has allowed some of the matter, which at first spread smoothly throughout space, to agglomerate through gravitation into the clumps that became galaxies, stars, and the relatively tiny objects we call "planets" and "moons." The Runaway Universe Since 1929, when Edwin Hubble discovered the expansion of the universe, astronomers have confronted the burning issue of whether this expansion will continue forever or whether the expansion may someday reverse itself into a contraction that might lead to another big bang. For more than eighty years, since Albert Einstein first created what still appears to be the correct theory of how space in the universe behaves, we have known that the amount of matter in the universe determines its future. Only one phenomenon might someday reverse the expansion to produce a universal contraction: gravity. Astronomers know that the gravitational attraction among all the objects in the universe has already slowed its expansion. The crucial question of whether this attraction will someday actually reverse the expansion, making the universe start to contract, finds its answer in the average density of matter. If that density, the amount of mass contained in a standard volume of space, exceeds a certain critical value, then the universe must eventually contract. If not, the expansion will continue indefinitely.     So astronomers believed until 1998. In that year, astronomers obtained startling new evidence from exploding stars (known by their Latin name as "supernovae"), seen in far-distant galaxies, that resurrected a long-discarded notion that Albert Einstein had created. In 1917, Einstein introduced an additional term, quickly named the "cosmological constant," into his equations describing the behavior of the cosmos. He did so for what seemed the best of reasons: the need to explain a "static universe," one in which space neither expands nor contracts. At that time, no astronomer suspected that a universal expansion might exist. Einstein, however, perceived that his equations, in the absence of a cosmological constant, imply that the cosmos must either expand or contract throughout cosmic history. His cosmological constant--not only permissible, but in a mathematical sense mandatory--allows the full spectrum of possibilities: expansion, contraction, or a static universe, with the latter permitted only if the constant has a single particular value. When Hubble's observations led to the discovery of the expanding universe, Einstein and his fellow scientists happily assigned the constant a value of zero, leaving it technically in existence but of no practical effect, and discarded the concept of a static universe.     For seven decades, this zero value seemed correct. Physicists who attempted to deduce the constant's value on theoretical grounds could do no better than to conclude that it ought either to be zero or to have values so enormously large that the universe could not exist. This analysis favored the zero value. Yet observations appear to have bypassed this reasoning. As astronomers improved their abilities to detect and to study supernovae that have exploded in galaxies billions of light-years beyond the Milky Way, they acquired the ability to discriminate between two crucial factors affecting the expansion: the amount of matter in the universe and the cosmological constant.     Whereas the gravitational forces among objects with mass act to slow the expansion, a cosmological constant greater than zero tends to make the cosmos expand more rapidly. This fact allows a cosmological constant with one particular value to balance the effect of gravity exactly--Einstein's original motivation for its introduction. Other nonzero values of the cosmological constant, however, imply a cosmos in which matter slows the expansion while the cosmological constant accelerates it, but the two effects do not balance each other exactly. By observing supernovae at immense distances, astronomers can hope to see the net effects of the contest between these two effects. A cosmological constant with a value greater than zero acts to increase the rate of expansion above what we would find if the constant equals zero. In that case, astronomers who observe supernovae in faraway galaxies should find that the exploding stars have greater distances from us than we would expect in a universe with a constant equal to zero. They can also measure the size of the cosmological constant, because a larger constant will have produced a greater acceleration of the expansion during the time since the supernovae exploded. This greater acceleration will have put still more "extra" distance between ourselves and the supernovae.     Early in 1998, two groups of supernova observers stood the cosmological world on its ear by announcing that their data analysis had in fact revealed a nonzero value for the cosmological constant. The implications for the future of the universe are tremendous--so significant, in fact, that in all that follows, we must bear in mind that the results from supernova observations must pass the test of skeptical scrutiny before we incorporate them in our inner fibers. If the cosmological constant has a nonzero value, the universe will expand forever, and, indeed, it will expand ever more rapidly as time goes by. Despite matter's heroic efforts to reduce the expansion rate to zero through gravitation, which have succeeded in slowing the expansion somewhat during the past 14 billion years, the cosmological constant's tendency to accelerate the cosmic expansion must eventually triumph.     The acceleration will win because the effects of gravity grow weaker as the universe expands, separating clusters of galaxies by greater distances and thus reducing their mutual gravitational attraction. In contrast, the cosmological constant keeps on coming: Every newly created cubic centimeter of space appears with the same amount of energy as all the cubic centimeters that already exist. A universe with a cosmological constant has the ability to produce new energy continuously, literally from nothing! The inevitable victory of acceleration over deceleration implies that in the long run, the universe will expand ever more rapidly. If the cosmological constant has a value greater than zero, then in epochs that lie tens and hundreds of billions of years in our future, the universe will expand far more rapidly than now--faster and still faster, so that the expansion will produce a "runaway," in which clusters of galaxies separate from one another at ever-greater velocities.     The runaway universe has produced relatively few enthusiasts in professional circles or among the general public. Aside from the astronomical difficulties of explaining why the cosmological constant should not equal zero, or why it should have the specific value implied by the recent observations of distant supernovae billions of light-years beyond the Milky Way, most of the public finds a bit distasteful the notion that the expansion will not only continue, but will in fact proceed at an ever-greater rate. To this, the supernova observers--and scientists in general--have a reply: Try to get used to it. If we seek to uncover a truth independent of our individual biases and beliefs, neither we nor professional scientists can let our desires rule cosmology, the study of the universe as a whole. What we must do, and what scientists love to do, is to pay close attention to the latest observations and their interpretation, probing for different explanations of the data. Only when we have satisfied ourselves that a nonzero cosmological constant offers by far the most coherent way to interpret the observational facts should we embrace the concept of the runaway universe. Even then, we must remain aware that new data and new interpretations may soon appear, causing us once again to question the framework within which we conceive the cosmos.     Let us examine, then, the cosmological observations and theories that have brought astronomers to the concept of the runaway universe, along with attempts to explain the accelerating expansion and the prospects for future resolution of the key cosmic issues. We shall meet observations of distant supernovae and the two teams of astronomers who compete to find the secrets of the cosmos, as well as other ways to attack these mysteries, including the bending of light by gravity, the formation of galaxies billions of years ago, and the faint afterglow of creation, which carries information about the universe at a time only a few hundred thousand years after the big bang. The mind-bending concepts involved in this examination will provide excellent mental exercise, and the results will prove so amazing that your friends and family will doubt what you have to tell them. Yet that is the cosmos you are meeting--not a parallel universe, but apparently our own. Excerpted from THE RUNAWAY UNIVERSE by Donald Goldsmith. Copyright © 2000 by Donald Goldsmith. Excerpted by permission. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.